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arXiv 1703.03099cond-mat.mtrl-scinlin.PS
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手征磁体和界面中Skyrmion的动力学和惯性:基于磁振子激发的线性响应方法

Dynamics and inertia of a skyrmion in chiral magnets and interfaces: A linear response approach based on magnon excitations

Shi-Zeng Lin

摘要:

考虑到所有的磁振子模式,我们推导出skyrmion动力学响应于一个弱的外部驱动。Skyrmion具有旋转对称性,并且磁振子模式可以用角动量来表征。对于弱畸变的Skyrmion,只有具有角动量$|m|=1$的磁振子模控制着Skyrmion拓扑中心的动力学。连续谱中的磁振子模决定了Skyrmion惯性。对于由磁场梯度或由电流产生的自旋转移矩驱动的skyrmion,动力学响应实际上是瞬时的。这证明了在Thiele的集体坐标方法中使用的刚性Skyrmion近似。对于由自旋霍尔力矩驱动的Skyrmion,力矩通过连续介质中的磁振子和阻尼耦合到Skyrmion运动,因此Skyrmion动力学在这种情况下表现出相当大的惯性。在旋转霍尔力矩的交流驱动下,Skyrmion的轨迹是椭圆。

英文摘要:

Taking all the magnon modes into account, we derive the skyrmion dynamics in response to a weak external drive. A skyrmion has rotational symmetry and the magnon modes can be characterized by an angular momentum. For a weak distortion of a skyrmion, only the magnon modes with an angular momentum $|m|=1$ govern the dynamics of skyrmion topological center. The skyrmion inertia is determined by the magnon modes in the continuum spectrum. For a skyrmion driven by a magnetic field gradient or by a spin transfer torque generated by a current, the dynamical response is practically instantaneous. This justifies the rigid skyrmion approximation used in Thiele's collective coordinate approach. For a skyrmion driven by a spin Hall torque, the torque couples to the skyrmion motion through the magnons in the continuum and damping, therefore the skyrmion dynamics shows sizable inertia in this case. The trajectory of a skyrmion is an ellipse for an ac drive of spin Hall torque.

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